The research plan is focused on neuropeptide processing carboxypeptidases. A major emphasis is on CPE, which has recently been proposed to play a role in peptide sorting into the secretory vesicle. We will evaluate this possibility using a variety of techniques. Another major emphasis is on carboxypeptidase D (CPD), an enzyme we recently discovered. It is likely that CPD processes peptides along with CPE, and this will be addressed in our future studies. A third area of emphasis is on three additional carboxypeptidase-like proteins which we have recently discovered (CPZ, CPX1, and CPX2). We will examine whether these novel proteins are able to process neuropeptides such as enkephalin and dynorphin, as well as test other possible functions. The results of these studies will provide a better understanding of the enzymes involved with peptide biosynthesis.